There actually are vaccines for chickens that protects against Bird flu with multiple in development. However they are nog mass produced yet and currently only small trials are staking place where they vaccinate all or part of the chickens on a single farm. Information about two of the vaccines van be found at https://www.ema.europa.eu/en/human-regulatory-overview/public-health-threats/avian-influenza-bird-flu
There actually are vaccines for chickens that protects against Bird flu with multiple in development. However they are nog mass produced yet and currently only small trials are staking place where they vaccinate all or part of the chickens on a single farm. Information about two of the vaccines van be found at https://www.ema.europa.eu/en/human-regulatory-overview/public-health-threats/avian-influenza-bird-flu